2009 年 8 巻 1 号 p. 24-30
Pyrobaculum islandicum is an ananaerobic hyperthermophilic archaeon that grows optimally at 100°C. We purified a NADH dehydrogenase from the membranes to homogeneity as analyzed by SDS-PAGE. The purified protein was suggested to comprise five subunits with molecular masses of 39 kDa, 37 kDa, 34 kDa, 31 kDa and 27 kDa, by SDS-PAGE analysis. The molecular mass of the native protein was estimated to be about 160 kDa by gel-filtration analysis. The optimal pH and temperature were 7.0 and above 80°C, respectively. The enzyme activity was shown to be highly specific to NADH, and the activity with NADPH was only 1.7% of the value with NADH.